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The isolation of a K562 cell line, K562(S)R, resistant to 1-beta-D-arabinofuranosylcytosine (ara-C)-mediated erythroid induction, is described. Ara-C (10-50 microM) inhibits cell growth of K562(S)R cells but is not able to activate the program of erythroid induction. This failure is associated with the lack in the increase of accumulation of epsilon-globin and gamma-globin mRNA sequences in ara-C-treated K562(S)R cells. This cell line could be of interest for studies focused on molecular mechanisms of activation of globin genes in K562 cells.

Forty-eight consecutive patients affected by chronic myelogenous leukemia (CML) Philadelphia (Ph) chromosome positive during the chronic phase of the disease underwent allogeneic bone marrow transplantation (BMT). Thirty-five patients had a follow-up over 12 months and were included in a cytogenetic study in order to evaluate the Ph clone eradication. In 25 cases, the Ph chromosome disappeared in all cytogenetic studies, and their hematologic picture is at present apparently normal. Ten patients showed cytogenetic relapse. In one case, the cytogenetic relapse was transitory without any clinical sign of the disease; in three cases, after a transitory cytogenetic relapse, a persistent relapse with clinical picture of progression of the disease occurred; in six cases cytogenetic and a clinical relapse were coincident. Structural chromosomal abnormalities other than Ph were temporarily seen in three cases. The so-called "nonrandom" chromosomal changes typical of the blastic phase were never detected. The reappearing Ph-positive clone spontaneously disappeared in three patients, and their hematologic picture reverted to complete chimerism. The present study confirms that the eradication of the Ph clone is often defective with BMT, and cytogenetic analysis can detect the competition between donor and residual host marrow. Furthermore, the karyotype evolution is different from that found in CML patients treated with conventional chemotherapy.

Spontaneous lymphoblastoid cell lines (LCLs) were established from the peripheral blood of 10 human immunodeficiency virus (HIV)-seropositive patients in order to investigate whether or not progression of the cells towards a malignant state could be traced. The LCLs studied displayed no differences in their surface phenotype, karyotype, and tumorigenicity in nude mice as compared with a wide panel of control LCLs. Furthermore, no c-myc rearrangement could be detected in any of the LCLs. However, 4 of the 10 LCLs derived from HIV-seropositive patients formed colonies in agar with a cloning efficiency of 0.1-0.9%. This percentage was much lower than that of a control neoplastic B cell line (50%), but consistently higher than that observed for a battery of spontaneous LCLs. The cells of a number of sublines that were derived from the agar colonies expressed new activation markers (CD10 and Bac-1) but did not induce tumors in nude mice or display chromosomal abnormalities. These sublines might comprise cells that have progressed towards a more markedly transformed state.

Both endothelial cells (EC) and fibroblasts, two discrete populations of hemopoietic stroma, are known to modulate the proliferation and differentiation of hemopoietic progenitors. Recent reports also demonstrated that EC stimulate the in vitro growth of fibroblasts via a soluble factor. This finding seems to support the hypothesis that EC may play a role in the pathogenesis of bone marrow fibrosis in myeloproliferative disorders (MD). We have studied the effects of the conditioned medium (CM) from human umbilical vein EC cultures, obtained in serum free conditions, on the growth of bone marrow fibroblasts from normal donors and from patients with MD. The results show that EC derived CM contains a factor which stimulates the proliferation of fibroblasts and that can act as an authentic growth factor by inducing "quiescent" fibroblasts to proliferate. Moreover, we found that this endothelial derived growth factor (EDGF) equally promotes the proliferation of both normal and pathological progenitors of bone marrow fibroblasts (CFU-F) by increasing both the number and the size of the colonies.

Leukemic cells with double minute (DM) chromosomes from an ANLL(M1) patient were found to carry 10-15 fold amplified c-myc sequences. The linked pvt-1-like locus was amplified at the same level, suggesting that the c-myc amplicon is at least 300 kb in size.

Cytogenetic study in a case of acute myelogenous leukemia revealed the presence of two identical dicentric marker chromosomes derived from an X with Xq13 breakpoints. Clinical and cytochemical findings suggest that the patient was affected by idiopathic acquired sideroblastic anemia before the acute leukemia.

Differentiation-dependent expression of enzyme loci was evaluated in two human leukemic cell lines, the pluripotent leukemia cell line K-562 and the promyelocytic-like cell line HL-60. Acetylcholinesterase, a marker of erythroid differentiation, was present in K-562 cells and absent in HL-60 cells. This difference between the two lines was apparently unrelated to dosage effect; other enzymes carried on trisomic chromosomes in K-562 cells did not show dosage effect. Acetylcholinesterase activity was higher in subclone K-562 (S), which shows higher expression of hemoglobin. Electrophoretic mobility of acetylcholinesterase from K-562 (S) was of fetal type.

One hundred patients with chronic myeloid leukemia (CML) submitted to bone marrow transplantation (BMT) were included in a cooperative cytogenetic study. Relapse (defined on the basis of hematological and cytogenetic findings) occurred in 24 (24%) patients at different intervals after BMT. In 18 of these patients (studied on average 3.3 times between BMT and relapse) no Ph-positive metaphases were detected before relapse. Sixteen (75%) of the patients relapsed with the same chromosomal pattern as that seen before BMT; eight patients, of whom five relapsed in blast crisis, showed additional chromosomal abnormalities resembling those seen in non-transplanted patients. One of these patients relapsed in cells of donor origin. After recognition of relapse, various hematological and cytogenetic patterns were observed. Four patients showed spontaneous reversion to normal (donor-type) chromosomes and hematology. Two other patients were followed for prolonged periods with hypercellular marrows with more than 50% Ph-positive cells but with normal peripheral blood values. The majority of patients proceeded to clinical relapse and required treatment with chemotherapy. We conclude that the isolated finding of a minority of Ph-positive metaphases after BMT should not be classified as relapse; for patients who do relapse, the sequence of cytogenetic and hematological events thereafter is variable.

Between 1979 and 1988, 86 patients with clinical and laboratory findings consistent with essential thrombocythemia (ET) were karyotyped at diagnosis. Four patients showed a Philadelphia chromosome and underwent myeloid blastic crisis 2.5-4.5 years later, strongly suggesting a diagnosis of chronic myeloid leukemia. A partial deletion of 13q was seen in another case evolving to leukemia a few months later. Five cases, with normal karyotypes at diagnosis, developed acute transformation after more than 5 years of chronic phase. Four of them showed unusual clonal karyotype abnormalities involving different chromosomal regions. The numerical abnormalities found were trisomy 22 in one case, and trisomy 8 and 19 in another, while structural changes included partial deletion of 5p, partial deletion of 6q, pericentric inversion of chromosome 12, and partial deletion of 20q. These abnormalities have not been previously reported in ET. This investigation confirms the absence of a specific cytogenetic marker for ET, and the infrequent transformation to acute leukemia, often with chromosomal clonal disorders.

We describe here a patient with Ph'-positive chronic myelogenous leukemia (CML) who developed a Ph'-negative blastic crisis. The blast DNA was analyzed on two different occasions, at the beginning of the blastic phase and at the end, shortly before the patient's death. Although cells from both samples had no Ph' chromosome marker (not even a masked one) we could detect a rearrangement of the bcr gene in the second DNA sample, using a '3'-bcr' probe. The same probe and a '5'-bcr' probe failed to detect any rearranged band in the first DNA sample. No rearrangement was identified at the c-myc and N-ras loci, while a slight c-myc amplification was evident in both DNA samples tested.